Conventionally, a capacitor is composed of two electrodes and a dielectric material interposed between these electrodes. As one of the electrodes of such a capacitor (hereinafter referred to as “one part electrode”), an electrode comprising one member selected from tantalum, aluminum, niobium, titanium and an alloy of these metals is known. Among these, tantalum is preferred because a capacitor fabricated can have various good performances and a relatively small capacitor can be manufactured. To this electrode, one end of an outgoing lead wire for obtaining electrical connection to the outside is connected. In the vicinity of the lead wire connected part, a dielectric layer equal to the dielectric layer formed on the one part electrode is usually formed. The construction material of the lead wire is tantalum and the shape of the lead wire is usually a cylindrical fine line.
When the one part electrode is reduced in the mass, the mass of the outgoing lead wire occupying in the capacitor becomes large relatively to the electrode. The mass unit price of tantalum fine line is higher than the unit price of tantalum electrode and for the purpose of cost reduction of the capacitor, a material low in the unit price is demanded. Niobium comes under such a material.
The density of niobium is about a half the density of tantalum and the output of niobium is larger than tantalum, therefore, the mass unit price of niobium is expected to be a half or less that of tantalum. However, when niobium is used for the outgoing lead wire, some capacitors fabricated suffer from poor heat resistance property. An attempt has been made to increase the thickness of the dielectric material formed on the one part electrode in order to solve this problem. The fabricated capacitor is, however, disadvantageously reduced in the capacitance.